program comb
integer::n,r,nfac,rfac,nrfac,ncr
write(*,*)"Enter n and r"
read(*,*)n,r
nfac=1
do i=1,n
nfac=nfac*i
end do
rfac=1
do i=1,r
rfac=rfac*i 
end do
nrfac=1
do i=1,n-r 
nrfac=nrfac*i 
end do 
ncr=nfac/(rfac*nrfac)
write(*,*)"nCr=",ncr
end program comb